Apple has pulled a stealth refresh of its iMac line, bringing faster processors, graphics, storage and Wi-Fi to the new desktops.

The new iMacs feature Intel's latest Haswell processors, the two 21.5" iMacs have base configurations of 2.7 GHz and 2.9 GHz, while the 27" iMacs start from 3.2 GHz and 3.4 GHz. All processors include Intel's Turbo Boost 2.0, which can automatically raise the speed of active cores. The faster graphics include the new Iris Pro integrated graphics on the lowest-end 21.5" iMac, Nvidia GeForce 700 cards are available on the higher-end 21.5" and both 27" iMacs.

All iMacs come with 802.11ac Wi-Fi, the latest and fastest version of the wireless protocol - your router will have to support it first though. They also feature PCIe-based flash storage, which Apple says makes Fusion Drive and all-flash storage options up to 50 percent faster than the previous generation. An all-flash 1TB storage option is available, but that will cost a cool S$1,400 more.

All iMacs come standard with 8GB of memory, two Thunderbolt and four USB 3.0 ports. They are available for order now on Apple's website. The new iMacs come ahead of the release of OS X Mavericks, which is rumored to launch next month alongside this year's new iPads.